There are two types of 911 ventilation system controls I am familiar with, with the only difference being one or two levers at the top. For 77 (and many other years), cars w/o air conditioning had two independent levers for fresh air and the fresh air fan. Cars with A/C had a single lever which when slid to the right first opened the fresh air ducts from the fan box, and then when moved further to the right engaged the fan speed settings.
This latter mechanism always made more sense to me since why would there be a need to have the fan running if the valves leading out of the fresh air fan box where shut?
Since I am retrofitting a non-A/C ventilation system in my car (
Retrofitting non-A/C ventilation ducts) , I started looking into this a bit deeper when deciding whether to replace the dash controls. I ran into this interesting piece of information from the 77 owner's manual (picture in red box):
So, can someone please explain how having the fresh air ducts closed (top left lever to left - "no fresh air supply from the outside"), and the fan at high speed (top right lever to the right) can provide "maximum ventilation of car interior, open center vents"? How is the air getting out of the fan box with the fresh air ducts leading out of the left and right side closed?
I thought I knew every last detail of this system, but there is something different about a non-A/C system that I am unaware of. I believe javadog's post in my thread above which shows a picture of the non-A/C system is providing some clues with the linkage on the splitter duct. I suppose once I get the splitter duct I ordered (2-3 weeks), this may be clearer.
btw, I know the ventilation system has been discussed here ad nauseam, but I did a search and couldn't find anything on this particular subject.
thanks for any insight,
Frank